Transparent glass pane provided with a surface structure

ABSTRACT

A method of manufacturing a transparent pane, in particular a glass pane, which includes on at least one of its main surfaces a surface structure including an assembly of specified individual motifs in relief, in particular pyramids, cones, or truncated cones, created by embossing or by rolling. A structure is created on the surface of the pane constituted by individual motifs, based on one or more basic motifs but which are distinguished from each other by their depth, their height, and/or the perimeter of their base area, and/or by the position of their peak with respect to their base. With this variation, formation of intensity peaks of the reflected light is prevented and at the same time a high quality of light trapping is obtained by panes suitable, for example, for solar applications.

The Invention relates to a pane, a method of manufacturing a transparentpane and a device for manufacturing a transparent pane and in particulara glass pane which is provided with a surface structure for capturinglight.

The invention also relates to panes which have such surface structures,a device or a tool which is suitable to the implementation of the methodas well as preferred uses of the panes.

From EPO493202B1 are known transparent panes provided with regularsurface structures in which a structure impressed in the substrate isformed of pyramid-shaped recesses that are identical to each other andwhich are separated from each other by distances smaller than thebiggest dimension of the recesses. The pyramids or truncated pyramidswhich are provided in them as a motif can be produced with a hexagonalor square base area but all have approximately plane side surfaces.

Combinations of embossing and of pyramids which protrude from theirbottom have also been described. In particular, good light diffusionproperties and a reduced visual detection of the presence of individualmotifs which form the structure is obtained in this way due to aharmonious overall matt surface appearance.

Moreover, there is known, from WO03/046617A1, the manufacture and use oftransparent plates (panes) provided with surface structures in the formof geometric relief which should improve the transmission of light andthe light efficiency in particular for panes which are combined withsolar cells (that is to say photoelectric cells or photovoltaic cells)and photovoltaic solar modules in solar collectors, flat plasmadischarge lamps, image projection screens and projectors. The motifs ofthe geometric structure can in particular be concave with respect to theoverall surface of the structured side of the pane, that is to say hotrolled into the initial substrate or formed in another appropriate way.In general, the motifs have a periodic shape, unlike that which isobtained by sandblasting or by etching methods. For technical productionreasons (traversing speed, adhesion of rolled material on the rolls,etc.) it is not however possible to reproduce this periodicity with thedesired accuracy. Moreover, undesirable periodic disturbances of theembossing operation can be added to it, for example due to dimensionaldeviations of the centering of the axes of the rolls when the rollingmanufacturing method is used.

Because of this, on these structured surface panes, an optical phenomenais established by which the incident light is reflected differently bypanes provided with the same surface motif and disposed or installedclose to each other in the same plane or even within one and the samepane. In practice, depending on the assembly position, one part of thesurface can reflect brilliantly and brightly whilst an immediatelyadjacent parallel part of surface has a matt appearance. Even throughthis effect is purely visual and aesthetic, it does not at all degradethe traversing of the light to the elements, detectors, etc., situatedon the other side of the pane.

The cause of the variation of the impression of brightness according tothe position on the pane is as follows.

Structures which are entirely regular in the ideal case have acharacteristic reflection motif in which, for a given angle of incidenceof light, the reflection takes place in specified directions and noreflection takes place in angular ranges which are adjacent to them. If,in a zone of the glass, because of the production tolerances mentionedabove, the structures are formed on the surface of the glass in a(slightly) different manner, the characteristic direction of reflectionof that zone of the glass is oriented in another direction (anotherangle). The consequence is that situations appear in which an observeris in the direction of reflection for one part of the glass but not inthe direction of reflection of the other part of the glass. Thus, onezone of the glass has a bright appearance (reflecting) and the other asa dark appearance. In principle, this effect also takes place on glasswith a smooth surface, but which is for example curved, which also has abright reflection appearance only at certain places for given positionsof the sun and of the observer.

However, it is possible to look for possibilities of giving theseglasses a regular appearance of the light reflection in a particularmounting case.

The external appearance of these surfaces should not however beessentially different from the regular structures available at present,and in particular the panes should be able to be used beside oneanother.

U.S. Pat. No. 4,411,493 discloses a pane for building windows which mustcontribute to energy saving both in summer (air-conditioning) and inwinter (heating). By a linear motif of parallel lines, there is obtainedwith this configuration a reflection or absorption behavior whichstrongly depends on the angle of incidence of the light.

Many cases are known of the use of surfaces that are chemically etchedor treated by sandblasting in order to give them more or less irregularstructures.

Fundamentally, there is known (see DE3805067A1 and DE4102984A1) thetechnique which consists in impressing random superficial structures onrolled surfaces using rolls on which random surface structures have beencreated. In all cases on continuously rolled substrates which are longerthan one roll revolution, these structures are repeated periodically asa result of the regular rotation of the roll.

The invention as claimed solves the above-mentioned problems.

The invention proposes glazing solving the abovementioned problems aswell as a method making it possible to impress, by embossing or rollinga surface of a transparent pane, a structure whose average lightreflection intensity depends as little as possible on the angle ofobservation. A device will also have to be created which is particularlywell suited for implementing the method.

Dispensing with the usual present-day method of embossing or rolling inwhich a very regular overall structure of identical motifs is obtained,according to the invention, the surface of the substrate to be treatedis embossed by a plurality of motifs identical or at least similar to acommon basic motif but with depths and/or base areas which vary.

Thus, on the variation due to the production of intrinsically identicalstructures on the embossed or rolled surface and which, in practice, canbe avoided only with non-negligible working, there is superimposed apredictable variation of the individual motifs or of structuralelements. In this way, a variation is obtained over wide angular rangesin the directions of diffusion of light during reflection. On the onehand, this has the effect of reducing the average absolute intensity ofthe reflection in each individual angle of reflection and, on the otherhand, in this way marked (or pronounced) transitions between thereflecting directions and the non-reflecting directions are avoided.

Globally, according to one embodiment, a more or less straightorientation of the individual embossed or rolled motifs is dispensedwith in favor of less regular orientations, for example in the form ofarcs of circle or of undulation, but, unlike irregular random structures(obtained for example by sandblasting or etching), a basic motif whichvaries to a greater or lesser degree is retained.

Thus, the pane (in particular made of glass) according to the inventionhas on at least one of its main surfaces a surface structure which isconstituted by the assembly of individual motifs in relief, inparticular pyramids, cones or truncated cones, able to be created byembossing or rolling, the surface of the pane comprising a structureconstituted by individual motifs based on one or more basic motifs, saidindividual motifs varying on the surface of the pane in their depth ortheir height or the perimeter of their base area or in the position oftheir peak with respect to their base (the term “or” used between thedifferent types of variations allows combinations of variations and issynonymous with and/or). The motifs are therefore at least partiallydifferent from each other. Thus, the motifs on the surface of the paneare similar in their shapes (for example, they are all four-sidedpyramids) but the orientation of their surfaces is not the same from onemotif to another. It is possible to consider that the variation in theorientation of a surface of a motif amounts to rotating this surfaceabout an axis perpendicular to the overall plane of the pane or about anaxis parallel with the overall plane of the pane, or a combination ofthese two rotations.

If a motif surface is rotated about an axis perpendicular to the panewhen moving from one motif to another, the result is that the base linesof these motifs when aligned form zigzag lines. If a motif surface isrotated about an axis parallel with the plate which moving from onemotif to another, the result is to vary the height or the depth of themotifs. The shape of the individual motifs varies in surface withrespect to the basic motif, but some basic motifs can of course be onthe surface.

The retention, as accurately as possible, of a basic motif isparticularly advantageous when, by a regular fashioning, an optimallight trapping (or capture) structure is approached as closely aspossible. In this case “light trapping” means a surface structure whichoptimizes the penetration of light into the substrate or into anabsorber installed beneath the substrate, for example a solar cell.

Fundamentally, the light trapping effect of a structured surface becomesbetter as the elements of the structure become more tightly compacted.Basic motifs which can be produced on the surface of a substrate asclosely to each other as possible or directly joined to each other, andtherefore for example pyramids or truncated pyramids which have a basearea which is at least triangular (at least three sides) but preferablyof the quadrilateral or hexagonal type and in particular a base area inwhich all of the sides are equal is preferred. As a variant, anddepending on the requirements and the design objectives, it is possiblehowever to use other basic motifs, for example cones or truncated cones,and to modify them in the way proposed by the invention. In this case,it will obviously not be possible to avoid small intermediate spaces.

Preferably, the individual motifs are directly adjacent to each other.

In the context of the invention, it is possible to produce on one andthe same surface of pane different basic motifs situated beside oneanother or in different groups. Moreover, it is possible to deliberatelyprovide definite separations between the basic motifs. They must howeverbe dimensioned such that one entire basic motif cannot be insertedbetween two basic motifs. The distance between the centers of the basicmotifs will therefore be less than double the dimensions of its sides.

All of these embodiments, both with regard to the surface of thesubstrate (in particular a pane) and the surface of the associatedfashioning tool (by embossing or rolling), are midway between anarrangement that is as regular as possible and an entirely randomirregular arrangement of motifs or of structures. In a way that issimilar to the expression “fuzzy logic”, it is also possible to refer toa deliberately fuzzy motif.

When, in the present description, the preferred manufacturing method ismentioned, namely by rolling only, other methods are not howeverexcluded, for example embossing using dies or casting in molds. It iseven possible to consider the use of surface structures according to theinvention in the pressure injection method for panes made of syntheticmaterials by giving an appropriate surface structure to a wall of thecavity of the injection casting mold.

According to one embodiment, the variation according to the invention ofthe individual motifs relates to their depth/height and more preciselyto their depth of penetration or their relief with respect to theideally smooth surface of a substrate, and/or the shape or the perimeterof the base areas of the individual motifs.

Studies by the inventor have shown that a random variation of the depthor of the height of the individual motifs makes it possible to bringabout, in defined conditions, a reduction of the reflection problemsmentioned at the beginning. The variation of the height and/or of thedepth provides a reflection curve which is flatter than that of theusual surface structures. Solely from a commercial point of view, thissolution is particularly advantageous because it can be achieved withmotifs of the same perimeter as those of the usual structures and itcannot therefore be distinguished from them with the naked eye.

However, this solution has certain limits. The depth of penetration ofthe individual motifs cannot be increased at will for technical reasons,because the available substrates are not of any thickness whatsoever(these thicknesses being between 3 and 6 mm) and furthermore, it is alsonecessary to take account of the problems of separation between thesubstrate and the structuring tool. Thus, for the lateral dimensions andthe thickness of glass currently used, depths of penetration greaterthan about 0.9-1.0 mm are difficult to achieve.

Consequently, the variation of the depth can be obtained only by areduction of an “optimal” depth. However, this results in a reduction ofthe angle of the sides of the structures and therefore a reduction ofthe light trapping effect by the structure and a reduction inefficiency, in particular in solar applications. A reduction of thelight trapping effect could furthermore result in new problems ofreflection reinforced at certain angles.

In fact it is necessary to note here that in particular for specialsolar applications, the intention is to optimize the light trappingeffect that can be obtained finally by embossings (negative or indentedmotifs) in the surface of the substrate. However, in the context of theinvention, its use on individual protruding motifs (which positivelyprotrude above the basic surface) and their combination with negativemotifs is in no way excluded.

In the case of a variation in the depth or in the height of the basicmotifs, it is possible for the deepest or highest points of theindividual motifs not to extend over a straight line; in particular theycan follow an oscillating line.

In certain cases of application, it is recommended to provide avariation of the base area (or of the lateral dimensions) of theindividual motifs which is possible alone or in combination with thedepth variations mentioned above. In concrete terms and by way ofexample, it is possible to deform an initially square pyramid base intoone with a diamond or parallelogram shaped perimeter, the direction ofthe deformation being able to follow the two diagonals. The sameobviously follows to the base areas of pyramids whose base is not aquadrilateral (triangular, hexagonal or not square). With saidcontrolled deformation, a modification of the angle of the lateralsurfaces of these pyramids is obtained both with respect to the idealsurface (or the overall surface of the substrate) and with respect tothe direction of rolling (in the case of the use of a rolling roll) oreven with respect to any straight line which extends along the surfaceof the glazing pane.

In particular, the basic motifs can be pyramids in which the anglesformed by the sides of the base areas are modified in steps.

In particular, in the case in which the base areas of the pyramids arequadrilaterals, it is possible to vary the basic motifs by variation ofthe angle included between the sides of the said base area, the saidsides then being able to comprise two alignment lines (FL, FL′) whichglobally extend perpendicular to each other and which are bothconstituted by non-parallel base sides attached to the pyramids andstarting from which the perimeters of the base areas of the pyramids areconstructed by parallel step-by-step displacement.

In particular, the alignment lines (FL, FL′) can be globally symmetricalwith respect to the global alignment line, which simply means thatglobally the same angles occur again between the lines FL and the globalalignment line as between the lines FL′ and the global alignment line.

Moreover, the alignment lines (FL, FL′) can follow a periodic undulationin their longitudinal development (that is to say in their globalalignment line).

Thus, in an alignment line, the base area sides of the motifs (pyramidsin particular) can be on either side of the global orientation of thealignment line.

In particular, the alignment lines (FL, FL′) can be constituted by theassembly of at least two groups of parts, the angular deviations withrespect to the global direction of the alignment line for one of the twogroups being oriented on one side of the global alignment line, and theangular deviations with respect to the global direction of the alignmentline for the other group being formed towards the other side of theglobal alignment line.

The deformations are also possible in the lateral surfaces of the actualindividual motifs, these lateral surfaces can also be curved.Furthermore, it is obviously also possible to modify non-polygonal(round or oval) individual motifs by the method according to theinvention and to bring them together in order to obtain an overallstructure which does not have reflection peaks.

In concrete terms, the angle of a lateral surface of a pyramid withrespect to the ideal surface becomes more acute at a depth that isassumed identical when the base area of that pyramid is deformed into adiamond shape. If depth variations are superimposed, it is no longerpossible to define dimensions and angles for each pyramid, and theglobal structure or the reflection direction or directions are veryclose to a random structure.

However, even on a random structure, the reflection peaks described atthe beginning cannot be excluded absolutely, but the embossed surfacestructure according to the invention makes it possible to avoid them toa very great degree and in a reproducible manner.

The variation of the basic motif can be achieved by varying the positionof the peak of the motifs with respect to their base. This isparticularly advantageous if it is not desired to vary the height ordepth of the motifs and if it is desired that the alignment lines arewell aligned in straight lines (particularly in the case of four-sidedpyramids whose base area is a right-angled quadrilateral. In fact,simply by modifying the position of the peak, the orientation of thesides of the pyramids is modified, but on the contrary, in appearance toan observer, the motifs appear, a priori, as all identical. Moreover, asthe depth or the height is not altered, it is possible to choose theoptimal pyramid height, that is to say the largest that the chosenmanufacturing process will allow, and this applies to all of the motifs.

The variations can be provided at will in small steps or also in suddenjumps and can be regular or irregular. They can be repeatedperiodically, even at periods smaller than the circumference of arolling roll. Thus, the surface of the rolling roller (or roller) canhave periodic repetitions of “groups of motifs”. It is thereforepossible for there to be several “repetition periods” on thecircumference of said roll.

The periodic variation deliberately applied to the angle of reflectionmust vary in its absolute amplitude to a greater degree than theundesirable variation (caused by production) that it serves to mask.

The same applies to the periodicity of the variation applieddeliberately, which must have a length as short as possible in order togive an optical appearance that is as homogeneous and as regular aspossible. In fact, when the repetition of the motif or the repetition ofthe groups of motifs extend over distances that are too long, it ispossible to perceive it with the naked eye as undulations or similar,even at great distances.

In concrete terms, in an advantageous embodiment of the invention, it ispossible to obtain an undulated development of the series of successiveindividual motifs which vary geometrically in steps, the length andamplitude of the undulations varying as a function of the step of saidvariations. If it is desired that the motifs should appear as identicaland as aligned as possible, it is possible to act only on the variationof their depth. As shown in FIG. 6, this nevertheless produces avariation of the orientation of the surfaces of the motifs, but inappearance the sides of the base areas of the motifs are all howeverwell aligned.

In the context of the invention, it is possible to combine a variationof depth of the motifs with at least one other type of variation, likethat of the perimeter of their base area, or that of the position oftheir peak with respect to their base. Thus the term “or” used to givethe types of variation possible (in particular in the claims) covers thecombinations of variations and is therefore synonymous with and/or.

With the help of appropriate measuring and simulation methods, it ispossible to demonstrate the effect of the surface structure according tothe invention on the reflection behavior. At the same time, thereremains a certain similarity with the regular motifs used beforehand,such that, fundamentally, panes produced by current-day methods andthose by the new way of producing these panes can be combined freely.

Fundamentally, the structured surfaces according to the invention couldalso obtain additional roughness by chemical or sandblasting means. Thistype of roughness of the surfaces typically creates (at microscopiclevel) small surface structures which are essentially smaller that thestructures according to the invention, which are of the order ofmagnitude of a few millimeters. However, tests have shown that in solarcells, the light trapping that the macroscopic structures according tothen invention aims to improve is degraded.

Even though the applications (photovoltaic, increasing the lighttrapping effect) of these surface structures mentioned here preferstructuring on just one side and on just one face, and that adouble-face structuring could even be harmful for the desired effect,the surface structure described here could obviously also, for adecorative purpose, be produced on both faces of a pane.

The invention also relates to the assembly comprising the pane accordingto the invention and an element capable of collecting the light energytraversing said pane, said element being placed facing said pane, saidpane comprising the surface structure on the opposite face to saidelement. The pane can therefore also have a structure on both faces butthis is not necessary. The surface structure is therefore imperativelyat least on the side opposite to that of the light energy collectorelement. The element can in particular be a photovoltaic cell or a body(such as a black body) intended to be heated by the light energy, suchas for example a ducting or reservoir containing water that is requiredto be heated. For the case in which the element is a photovoltaic cell,the pane and the element are generally juxtaposed, a resin having arefractive index greater than that of the material constituting the panebeing placed if necessary between the pane and said photovoltaic cell.

A device according to the invention for the purpose of implementing themanufacturing method of these panes will comprise at least one tool (aroll or a flat embossing surface, for example the wall of a recess andof an injection mold) whose surface has a negative shape of thestructure which must be impressed in the surface of the pane by contactwith the tool.

In any case, the plastically non-deformable material of the pane israised to high temperature in contact with the tool and, by plasticdeformation, the structuring which is defined by the tool progressivelyincreases in the contact surface. The tolerances mentioned above withrespect to an ideal structure obviously cannot be avoided, but they canbe reduced by harmonization of the detailed structures of the tool withthe behavior of the particular material of the pane.

When glass panes are used, they will be chemically or thermally hardenedaccording to requirements after having impressed the structure.

Other details and advantages of the subject of the invention will emergefrom the drawing of an example embodiment and from its description givenbelow.

In the illustrations, which are simplified and not to scale:

FIG. 1 shows a light intensity diagram of the reflection plotted withrespect to a horizontal angle of observation for a constant verticalangle of observation, for a surface structure according to the prior art(aligned pyramids with square bases) and for a simulated surfacestructure according to the invention, in direct comparison,

FIG. 2 shows another light intensity diagram of the reflection plottedto the horizontal angle of observation for a constant vertical angle ofobservation for a simulated surface structure according to the inventionin which the quadrilateral pyramid base area of the embossing has beendeformed into diamond shapes having different angles,

FIGS. 3 a to 3 c show a comparison between the optical appearance of anexisting motif and an embodiment according to the invention,

FIG. 4 shows an enlarged view of a surface structure according to theinvention with variation of the perimeters of the base area of theindividual motifs or basic motifs and

FIG. 5 shows a cross section through a part of a pane provided with thesurface structure according to the invention in order to show thevariation of the depth of the individual elements of this structure forconstant lateral dimensions.

FIG. 6 shows the pane of FIG. 5 struck by parallel solar rays and showsthe variation of the orientation of the pyramid sides when moving fromone motif to another.

FIG. 7 shows juxtaposed motifs of a pane according to the invention,seen in a direction perpendicular to its surface, the motifs all havinga square base, but the point of said motifs varying position withrespect to the base areas of the pyramids.

For the measurements and simulations which have provided the resultsshown in FIGS. 1 and 2, the following assumptions have been made:

-   -   the surface in question (structured) of the pane is situated at        an angle of 35° to the horizontal,    -   the solar light strikes this surface at an angle of 38° to the        vertical,    -   the observer looks at this surface at an angle of −10° to the        horizontal and he turns around a fixed point of vision along a        horizontal arc. This arc is shown on the “angle of observation”        axis.

In this way there has been simulated the fitting of structured panes onthe surface of an inclined roof which is exposed to a defined solarradiation, an observer passing on the flat ground in front of this roof(of a house) and observing the variations of intensity of the reflectedlight.

In FIG. 1 can be seen two curves of different simulation of theintensity of the reflected light at an angle of observation of between−90° and +90°. As stated above, the representation of reflectionintensities at this angle of observation however relates to a constantheight of the observer's eyes with respect to the imaginary surface ofthe roof (which carries the reflecting surface) and to a constantposition of the sun during the displacement of the observer from −90° to+90°.

Curve 1 (the reference curve) shows in these conditions a sharp point(thinner, more pointed) at an angle of observation of 30°. This curverepresents the reflection of a surface structure which is constituted bynon-variable individual motifs. The point of this reflection curve formsthe strong reflection angle of the surface structure which theobserver's eye perceives at that specific angle of observation. Clearly,the intensity of the reflection reduces very greatly as soon as theangle of observation varies slightly. This explains the phenomenonexplained at the beginning of very irregular reflection of platessituated beside one another or of adjacent zones in one and the sameglass plate.

It can be seen that curve 2 has a much flatter shape. It has beendetermined by optical simulation of a surface structure according to theinvention which is constituted by the assembly of individual motifswhose base areas have variable parameters. This will be described againin more detail below.

FIG. 2 shows clearly that in a narrow defined range of angle ofobservation, the intensity of reflection greatly depends on the shape ofthe base area of the pyramids (diamonds). This diagram contains severalmeasurement curves of simulated surface structures which are allconstituted by the assembly of identical pyramids (basic motifs), butthe angle included between the sides of the parallelogram-shaped baseareas is modified from one curve to another, and this is so from 75° to90°, passing though 82°. The curves are all drawn with the associatedincluded angle. All of the angles of opening are obviously measured inthe same direction.

In the same simulation conditions as in the curves described here, forthe included angle of 105°, it is observed that a fine (pointed)reflection peak is no longer obtained. The corresponding curve has nothowever been shown here.

At an included angle of 75°, it is possible to see a distinct point(absolute maximum) of intensity of the reflection at an observationangle of about 40°.

Another relative maximum is situated at an observation angle of about−10°.

At an angle of opening of 82°, an absolute maximum is observed at anobservation angle of about 35°, but beside that latter there is nolonger any relative sharp maximum.

At an included angle of 90°, there is an absolute maximum at about 25°and a relative maximum at about −40°.

It can be seen that the points of the measured curves already shiftaccording to the observation angle because of the modification of theangle. They distinctly flatten as the observation angle increases.

It is also recalled that in this representation, and similarly for FIG.1, the assumption has been made that the angle of elevation/angle ofincidence of the sun is constant, and that when the height ofobservation is modified, other reflection peaks are also obtained.

The average curve indicated by ø, which fictitiously gives thedevelopment of the intensity for a surface structure constituted by theassembly of different individual motifs, is much flatter than thereference curve (FIG. 1) which was determined on the existing product.On the one hand the result of this is that the reflection intensity isgreatly reduced for the angle of observation of reflection but that thereflection depends much less strongly on the angle of observation. Smallmodifications of the observation angle, whether in the plane or inheight, no longer give rise to modifications of the reflected image thatare too abrupt.

FIGS. 3 a, 3 b and 3 c show a comparison between parts of a flat glassproduced and marketed by the applicant under the brand name “Albarino P”and having regular surface structures (FIG. 3 a) and a part with asurface structure according to the invention (FIG. 3 c). The structuralcharacteristics or basic motifs, namely pyramids impressed in thesurface of a glass pane, are represented here only by their perimeters.The length of a real pyramid side is about 2.5 mm for a comparativemotif. In the known product, all of the pyramids are of the same size,to within the technical manufacturing capabilities, and have the sameperimeter and the same depth. In order to improve visibility, thelateral sides of the pyramids which penetrate in depth have not beenshown, only the edges or sides of the base area which are situatedsubstantially in the overall surface of the pane have been shown.

In the following text, sides of pyramids or sides will not be mentioned,that is to say the lateral surfaces (triangular) of the pyramids, butsimply lines of the sides which are shown in a simplified manner inFIGS. 3 a to 3 c and 4 of the base areas of these pyramids.

The difference between the “conventional” motif and the motif accordingto the invention can be detected on real panes only after a morein-depth examination. In comparison with a real motif in a straightregular line, the motif according to the invention is deformed only inan almost invisible manner. It can however be seen with the naked eyethat the external edges and/or the alignment lines of the part shown inFIG. 3 c oscillate slightly with respect to the structure according tothe invention, whereas the known structure has lateral or alignmentlines that are straight lines.

The expression “alignment lines” here refers in a simplified manner tothe lines which are formed by the successive identical sides of pyramidsdisposed directly one behind the other in rows. In FIG. 3 a, two arrowsindicate these alignment lines.

By way of example of the production according to the invention of thedeformation of the alignment lines and therefore of the base areas ofthe pyramids, it is possible to give the following rules.

In the present example, the fundamental orientation of all of thealignment lines forms, as in the known structure of FIG. 3 a, an angleof 45° to the horizontal (of the figure). In other words, a link betweenthe two end points of alignment lines has at least approximately thisangle of 45°.

According to the invention, the longitudinal directions of the sides ofthe successive pyramids along each alignment line are modified in steps,but their lengths remain unchanged. In other words, according to theinvention, a variation of the angle of the individual sides of thepyramids is superimposed on the general or global orientation of thealignment lines which results in the undulation of the alignment line inFIGS. 3 b and 3 c.

Globally, two successive pyramid sides do not have the same angularposition or the same setting angle (Anstellwinkel in German) (that is tosay the same orientation) but follow each other in a zigzag, but withineach alignment line there are only obtuse angles.

In an advantageous embodiment of the invention, the orientations(setting angles) of two groups of pyramid sides are modified accordingto different rules. The individual lines of these two groups are thenassembled in an alternating manner in order to obtain an alignment line.In this way a continuous zigzag line is obtained upon which anundulation is superimposed. Thus, if the pane is looked at straight on,it is possible to see, on the one hand, the zigzag when moving from onepyramid to another and, on the other hand, on a larger scale, a globalundulation of the alignment lines.

In the example shown in FIG. 3 c, the first group is constituted byeleven pyramid sides which, starting from a setting angle of 35°, aremodified in steps of two degrees up to a setting angle of 45° and thenreturn to a setting angle of 35°.

The second group is constituted by eleven other pyramid sides which,starting from a setting angle of 45°, are modified in steps of twodegrees up to a setting angle of 55° and then return to an angle of 45°.

The two groups therefore have an angular range of 10° with respect tothe basic dimension (direction) of 45°, each group containingdifferences only in one direction (and therefore a setting angle whichis either ≧45° or ≦450).

By combining these two groups the upper alignment line FL shown in FIG.3 b is obtained, which is constituted by 22 individual pyramid sides ofthe same length.

A second alignment line FL′ which extends globally in a directionperpendicular to the first one (shown at the bottom in FIG. 3 b) iscreated symmetrically to the alignment line FL on the horizontal axis.The expression “globally perpendicular” here means that the global linksalready mentioned between the end points of two alignment lines areperpendicular to each other.

In FIG. 3 c, it is seen that in order to create the surface structureaccording to the invention with “regularly deformed” pyramid elements,the two alignment lines FL and FL′ assembled by their corners at theirends in FIG. 3 b are multiplied by parallel displacement along the sideof a pyramid. Each time, an end of the displaced alignment line isplaced exactly at the transition between two adjoining pyramid sides. Inthis way the resultant orientation of the parallel displacement isnecessarily not always the same but depends on the angle of the pyramidside in question. Even though the displaced alignment line alwaysretains the same length, the series of free ends of a series of parallelalignment lines exhibits the same profile of an alignment line whichextends in a zigzag manner. This has been shown clearly in FIG. 3 c bythe two outer closing alignment lines. It can be seen clearly that thealignment lines have been produced with a periodic undulation which canbe continued with no problems on larger surfaces.

It is obvious that these step by step variations of the base areas arealso possible with basic motifs that are not quadrilateral. In the caseof basic motifs with a triangular perimeter (triangular pyramids), amodification of the length of at least one side of the triangle couldnot however be avoided. Globally, because of the visual balance over theknown panes, an embodiment with quadrilateral basic motifs is preferred.

FIG. 4 once again shows the overall appearance of a structured surfaceaccording to the invention obtained with the construction method shownin FIG. 3 c. Three pyramid base areas of the motif have been shown inthe form of enlarged diamonds. They represent extreme deformations andan intermediate case. In the overall pattern, these shapes are notdirectly adjacent and can be separated from each other by one or moreindividual motifs which exhibit intermediate stages of the deformation,such that globally progressive transitions are obtained and thereforeundulating or zigzag lines that are not very extreme.

With a plurality of macro-elements directly adjacent to each other,whole and jagged (on their edges) shown in FIG. 4, it is possible tostructure any “endless” surface without joins, as in the conventionalvariant shown in FIG. 3 a.

FIG. 5 again shows an example of a possible variation of the depth ofpyramids formed by embossing. On a short part of a pane V embossedaccording to the invention, it can be seen that the depth of thepyramids disposed immediately beside one another is modified such thattheir deepest points can be connected to each other by an undulatingline W. Thus is it clear that for a same base area of the pyramids, theorientation of their lateral surfaces with respect to the global surfaceS of the pane also varies. This is more particularly conveyed with thehelp of FIG. 6 which shows parallel solar rays 3 coming at an angle ofincidence to the pane. The sides of the pyramids have been extended bystraight lines in order to show clearly that these straight lines arenot parallel and form different angles alpha1, alpha2 and alpha3 withthe global plane of the plate. The solar rays therefore strike thesurfaces of the pyramids at different angles and they are therefore alsoreflected differently from one pyramid to another.

The perimeters of the pyramids have been drawn here in an idealizedmanner, without deviations caused by production.

It is obvious that a pure depth variation could be produced in arelatively simple manner even with non-quadrilateral basic motifs asalready mentioned.

FIG. 7 shows twelve juxtaposed motifs of a pane according to theinvention, seen in a direction perpendicular to its surface. It can beseen that the basic motif is a pyramid with four sides, that is to sayone whose base area is a quadrilateral. In this case, all of theindividual motifs have the same base area and the same depth. Because ofthis, the base lines of the motifs are all aligned and the alignmentlines are straight lines. In the case shown, the alignment lines formtwo groups of lines perpendicular to each other. What changes from onemotif to another is, firstly, the position of the peak 4 of the pyramidswith respect to their respective bases. This variation of position givesrise to the variation of the orientations of the surfaces of the sidesof the pyramids when moving from one pyramid to another. Because ofthis, each pyramid reflects light slightly differently in comparisonwith its neighbor. This embodiment is very aesthetic because of thealignment of the base lines of the pyramids. For this type of motif, itcan be said that the basic motif is a square-based pyramid whose peakvaries in position with respect to the base.

1-23. (canceled) 24: An assembly comprising: a transparent pane; and anelement configured to collect light energy traversing the pane, theelement facing the pane, the pane comprising a surface structure on atleast one of its main surfaces placed on an opposite face to theelement, wherein the surface structure includes an assembly ofindividual motifs in relief that are based on one or more basic motifs,the individual motifs varying on the surface of the pane in their depthor their height or their perimeter of their base area, or in a positionof their peak with respect to their base. 25: The assembly as claimed inclaim 24, wherein the individual motifs are pyramids, cones, ortruncated cones. 26: The assembly as claimed in claim 24, wherein thebasic motifs are pyramids whose base area is at least three-sided orquadrilateral. 27: The assembly as claimed in claim 24, wherein theindividual motifs are directly adjacent to each other. 28: The assemblyas claimed in claim 24, wherein in a case of a variation in the depth orthe height of the basic motifs, deepest or highest points of theindividual motifs do not extend over a straight line, or follow anoscillating line. 29: The assembly as claimed in claim 24, wherein thebasic motifs are pyramids in which angles formed by the sides of thebase areas are modified in steps. 30: The assembly as claimed in claim29, wherein the base areas of the pyramids are quadrilaterals, and basicmotifs are created by variation of an angle formed by sides of the baseareas, two alignment lines globally extending perpendicular to eachother and that are both constituted by non-parallel base sides attachedto the pyramids and starting from which the perimeters of the base areasof the pyramids are constructed by parallel step-by-step displacement.31: The assembly as claimed in claim 30, wherein the alignment lines aresymmetrical. 32: The assembly as claimed in claim 30, wherein thealignment lines are formed with a periodic undulation of theirlongitudinal development. 33: The assembly as claimed in claim 30,wherein, in an alignment line, the base area sides of the pyramids areon either side of the global orientation of the alignment line. 34: Theassembly as claimed in claim 33, wherein the alignment lines include anassembly of at least two groups of parts, angular deviations withrespect to the global direction of the alignment line for one of the twogroups being oriented on one side of the global alignment line, andangular deviations with respect to the global direction of the alignmentline for the other group being formed towards the other side of theglobal alignment line. 35: The assembly as claimed in claim 24, whereinthe individual motifs are impressed in a form of recesses in a materialof the pane. 36: The assembly as claimed in claim 24, wherein theindividual motifs are created in a form of reliefs protruding withrespect to the surface of the pane. 37: The assembly as claimed in claim24, wherein the two surfaces of the pane include a surface structure.38: The assembly as claimed in claim 24, wherein the element is aphotovoltaic cell. 39: The assembly as claimed in claim 38, wherein thepane and the element are juxtaposed, a resin having a refractive indexgreater than that of the material constituting the pane being placed asneeded between the pane and the photovoltaic cell. 40: A transparentpane having on at least one of its main surfaces a surface structureincluding an assembly of individual motifs in relief that are based onone or more basic motifs, the individual motifs varying on the surfaceof the pane in their depth or their height or the perimeter of theirbase area, wherein the basic motifs are pyramids in which angles formedby sides of the base areas are modified in steps. 41: The pane asclaimed in claim 40, wherein the base areas of the pyramids arequadrilaterals, and basic motifs are created by variation of an angleformed by the sides of the base areas, two alignment lines globallyextending perpendicular to each other and that are both constituted bynon-parallel base sides attached to the pyramids and starting from whichthe perimeters of the base areas of the pyramids are constructed byparallel step-by-step displacement. 42: The pane as claimed in claim 41,wherein the alignment lines are symmetrical. 43: The pane as claimed inclaim 41, wherein the alignment lines are formed with a periodicundulation of their longitudinal development. 44: The pane as claimed inclaim 40, wherein, in an alignment line, the base area sides of thepyramids are on either side of the global orientation of the alignmentline. 45: The pane as claimed in claim 44, wherein the alignment linesinclude an assembly of at least two groups of parts, angular deviationswith respect to the global direction of the alignment line for one ofthe two groups being oriented on one side of the global alignment line,and angular deviations with respect to the global direction of thealignment line for the other group being formed towards the other sideof the global alignment line. 46: A transparent pane comprising: on atleast one of main surfaces of the pane a surface structure including anassembly of individual motifs in relief, wherein the individual motifsare based on one or more basic motifs, the individual motifs varying onthe surface of the pane in a position of their peak with respect totheir base. 47: The pane as claimed in claim 46, wherein the pane ishardened thermally or chemically. 48: A method of manufacturing the paneas claimed in claim 46 by embossing or by rolling. 49: Use of atransparent pane, the pane comprising on at least one of its mainsurfaces a surface structure including an assembly of individual motifsin relief, wherein the individual motifs are based on one or more basicmotifs, the individual motifs varying on the surface of the pane intheir depth or their height or the perimeter of their base area, or in aposition of their peak with respect to their base, as a pane forcovering construction elements intended for using solar light.